The subject matter of the present invention relates to a perforating apparatus, and in particular, to a pivot gun through-the-tubing perforating apparatus, the pivot gun being adapted to be disposed within a tubing and including a plurality of rotatable shaped charges and a pair of release means, such as a pair of explosive bolts. The charges are adapted to rotate from a stored position to a deployed position and slidingly engage a stationary detonating cord during the rotation to the deployed position. The pair of release means each function to provide a release; that is, the charges pivot from the stored position to the deployed position in response to a release provided by the first release means; and, in the event the charges fail to detonate, the gun may more easily be retrieved from within the tubing when a release is provided by the second release means.
U.S. Pat. No. 4,961,365 to Rytlewski, assigned to the same assignee as that of the present invention and incorporated herein by reference, discussed several problems associated with prior art rotating charge perforating guns (otherwise known as pivot guns), which problems created a need for a new type of pivot gun. The Rytlewski patent satisfied this need by disclosing a pivot gun perforating apparatus having a mechanical link retaining mechanism for contacting and holding a detonating cord to a top of each charge and enabling the charges of the gun to pivot in response to a pull on a pullrod connected to each charge. Since the detonating cord is connected to the top of each charge, the cord moves in response to a corresponding rotational movement of the top of the charge. However, although the Rytlewski perforating apparatus satisfactorily satisfied the need, under certain circumstances, it may be more desirable to allow the detonating cord to remain stationary during rotational movement of the charges. Furthermore, in the Rytlewski patent, the implementation for producing the pull on the pullrod and rotating the charges was not disclosed.